Src homology 2 (SH2) domain found in B-cell linker (BLNK) protein and SH2 domain-containing leukocyte protein of 76 kDa (SLP-76); BLNK (also known as SLP-65 or BASH) is an important adaptor protein expressed in B-lineage cells. BLNK consists of a N-terminal sterile alpha motif (SAM) domain and a C-terminal SH2 domain. BLNK is a cytoplasmic protein, but a part of it is bound to the plasma membrane through an N-terminal leucine zipper motif and transiently bound to a cytoplasmic domain of Iga through its C-terminal SH2 domain upon B cell antigen receptor (BCR)-stimulation. A non-ITAM phosphotyrosine in Iga is necessary for the binding with the BLNK SH2 domain and/or for normal BLNK function in signaling and B cell activation. Upon phosphorylation BLNK binds Btk and PLCgamma2 through their SH2 domains and mediates PLCgamma2 activation by Btk. BLNK also binds other signaling molecules such as Vav, Grb2, Syk, and HPK1. BLNK has been shown to be necessary for BCR-mediated Ca2+ mobilization, for the activation of mitogen-activated protein kinases such as ERK, JNK, and p38 in a chicken B cell line DT40, and for activation of transcription factors such as NF-AT and NF-kappaB in human or mouse B cells. BLNK is involved in B cell development, B cell survival, activation, proliferation, and T-independent immune responses. BLNK is structurally homologous to SLP-76. SLP-76 and (linker for activation of T cells) LAT are adaptor/linker proteins in T cell antigen receptor activation and T cell development. BLNK interacts with many downstream signaling proteins that interact directly with both SLP-76 and LAT. New data suggest functional complementation of SLP-76 and LAT in T cell antigen receptor function with BLNK in BCR function. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1040660804 413 DAEEEAGVYKKVWYASGCDRKTAEDALIRSAKDGSFLLRKSSGVDAQQPYTLVVFYNSRVYNIPVRYIASTKQYSLGKEK 492
Cdd:cd09929     1 SAEEEADLLPKEWYAGNIDRKEAEEALRRSNKDGTFLVRDSSGKDSSQPYTLMVLYNDKVYNIQIRFLENTRQYALGTGL 80

                          90       100       110       120
                  ....*....|....*....|....*....|....*....|.
gi 1040660804 493 QGEERFSSVCDMIENHQKNPLVLVDSLSNTKDSTKLRHAVK 533
Cdd:cd09929    81 RGEETFSSVAEIIEHHQKTPLLLIDGKDNTKDSTCLLYAAG 121

Src homology 2 (SH2) domain found in B-cell linker (BLNK) protein and SH2 domain-containing leukocyte protein of 76 kDa (SLP-76); BLNK (also known as SLP-65 or BASH) is an important adaptor protein expressed in B-lineage cells. BLNK consists of a N-terminal sterile alpha motif (SAM) domain and a C-terminal SH2 domain. BLNK is a cytoplasmic protein, but a part of it is bound to the plasma membrane through an N-terminal leucine zipper motif and transiently bound to a cytoplasmic domain of Iga through its C-terminal SH2 domain upon B cell antigen receptor (BCR)-stimulation. A non-ITAM phosphotyrosine in Iga is necessary for the binding with the BLNK SH2 domain and/or for normal BLNK function in signaling and B cell activation. Upon phosphorylation BLNK binds Btk and PLCgamma2 through their SH2 domains and mediates PLCgamma2 activation by Btk. BLNK also binds other signaling molecules such as Vav, Grb2, Syk, and HPK1. BLNK has been shown to be necessary for BCR-mediated Ca2+ mobilization, for the activation of mitogen-activated protein kinases such as ERK, JNK, and p38 in a chicken B cell line DT40, and for activation of transcription factors such as NF-AT and NF-kappaB in human or mouse B cells. BLNK is involved in B cell development, B cell survival, activation, proliferation, and T-independent immune responses. BLNK is structurally homologous to SLP-76. SLP-76 and (linker for activation of T cells) LAT are adaptor/linker proteins in T cell antigen receptor activation and T cell development. BLNK interacts with many downstream signaling proteins that interact directly with both SLP-76 and LAT. New data suggest functional complementation of SLP-76 and LAT in T cell antigen receptor function with BLNK in BCR function. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1040660804 413 DAEEEAGVYKKVWYASGCDRKTAEDALIRSAKDGSFLLRKSSGVDAQQPYTLVVFYNSRVYNIPVRYIASTKQYSLGKEK 492
Cdd:cd09929     1 SAEEEADLLPKEWYAGNIDRKEAEEALRRSNKDGTFLVRDSSGKDSSQPYTLMVLYNDKVYNIQIRFLENTRQYALGTGL 80

                          90       100       110       120
                  ....*....|....*....|....*....|....*....|.
gi 1040660804 493 QGEERFSSVCDMIENHQKNPLVLVDSLSNTKDSTKLRHAVK 533
Cdd:cd09929    81 RGEETFSSVAEIIEHHQKTPLLLIDGKDNTKDSTCLLYAAG 121

SAM domain of SLP76 subfamily; SAM (sterile alpha motif) domain of SLP76 (SH2 domain-containing leukocyte protein 76), also known as LCP2 (Lymphocyte cytosolic protein), subfamily is a protein-protein interaction domain. Proteins of this group have an N-terminal SAM domain, 3 phosphotyrosine motifs, a proline-rich region and a C-terminal SH2 domain. They are scaffold proteins involved in protein complex formation. The complexes play a role in T-cell receptor mediated signaling pathways such as integrin activation, cytoskeletal organization, MARK activation, and calcium flux. SAM domain deleted SLP76 knockin mice show a number of defects, including partially blocked thymocyte development, impaired positive and negative thymic selection and changes in T-cell receptor mediated signaling.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 1040660804  11 GWSPAQVASFLNQNNMRECAEAVQRNRIDGGRLLTLSDSDLNKFSFIHRPQLQKIVQDIKKND 73
Cdd:cd09522     5 GWNPHSLADYFKKLNLKGCDKVVKKSNINGQRFLNMTENDIQKFPKLHVPFISKICQEINKNE 67

SAM domain (Sterile alpha motif);

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 1040660804  10 EGWSPAQVASFLNQNNMRECAEAVQRNRIDGGR-LLTLSDSDLNKF---SFIHRPQLQKIVQDIK 70
Cdd:pfam07647   2 ESWSLESVADWLRSIGLEQYTDNFRDQGITGAElLLRLTLEDLKRLgitSVGHRRKILKKIQELK 66

Src homology 2 (SH2) domain found in B-cell linker (BLNK) protein and SH2 domain-containing leukocyte protein of 76 kDa (SLP-76); BLNK (also known as SLP-65 or BASH) is an important adaptor protein expressed in B-lineage cells. BLNK consists of a N-terminal sterile alpha motif (SAM) domain and a C-terminal SH2 domain. BLNK is a cytoplasmic protein, but a part of it is bound to the plasma membrane through an N-terminal leucine zipper motif and transiently bound to a cytoplasmic domain of Iga through its C-terminal SH2 domain upon B cell antigen receptor (BCR)-stimulation. A non-ITAM phosphotyrosine in Iga is necessary for the binding with the BLNK SH2 domain and/or for normal BLNK function in signaling and B cell activation. Upon phosphorylation BLNK binds Btk and PLCgamma2 through their SH2 domains and mediates PLCgamma2 activation by Btk. BLNK also binds other signaling molecules such as Vav, Grb2, Syk, and HPK1. BLNK has been shown to be necessary for BCR-mediated Ca2+ mobilization, for the activation of mitogen-activated protein kinases such as ERK, JNK, and p38 in a chicken B cell line DT40, and for activation of transcription factors such as NF-AT and NF-kappaB in human or mouse B cells. BLNK is involved in B cell development, B cell survival, activation, proliferation, and T-independent immune responses. BLNK is structurally homologous to SLP-76. SLP-76 and (linker for activation of T cells) LAT are adaptor/linker proteins in T cell antigen receptor activation and T cell development. BLNK interacts with many downstream signaling proteins that interact directly with both SLP-76 and LAT. New data suggest functional complementation of SLP-76 and LAT in T cell antigen receptor function with BLNK in BCR function. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1040660804 413 DAEEEAGVYKKVWYASGCDRKTAEDALIRSAKDGSFLLRKSSGVDAQQPYTLVVFYNSRVYNIPVRYIASTKQYSLGKEK 492
Cdd:cd09929     1 SAEEEADLLPKEWYAGNIDRKEAEEALRRSNKDGTFLVRDSSGKDSSQPYTLMVLYNDKVYNIQIRFLENTRQYALGTGL 80

                          90       100       110       120
                  ....*....|....*....|....*....|....*....|.
gi 1040660804 493 QGEERFSSVCDMIENHQKNPLVLVDSLSNTKDSTKLRHAVK 533
Cdd:cd09929    81 RGEETFSSVAEIIEHHQKTPLLLIDGKDNTKDSTCLLYAAG 121

SAM domain of SLP76 subfamily; SAM (sterile alpha motif) domain of SLP76 (SH2 domain-containing leukocyte protein 76), also known as LCP2 (Lymphocyte cytosolic protein), subfamily is a protein-protein interaction domain. Proteins of this group have an N-terminal SAM domain, 3 phosphotyrosine motifs, a proline-rich region and a C-terminal SH2 domain. They are scaffold proteins involved in protein complex formation. The complexes play a role in T-cell receptor mediated signaling pathways such as integrin activation, cytoskeletal organization, MARK activation, and calcium flux. SAM domain deleted SLP76 knockin mice show a number of defects, including partially blocked thymocyte development, impaired positive and negative thymic selection and changes in T-cell receptor mediated signaling.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 1040660804  11 GWSPAQVASFLNQNNMRECAEAVQRNRIDGGRLLTLSDSDLNKFSFIHRPQLQKIVQDIKKND 73
Cdd:cd09522     5 GWNPHSLADYFKKLNLKGCDKVVKKSNINGQRFLNMTENDIQKFPKLHVPFISKICQEINKNE 67

Src homology 2 (SH2) domain found in Abelson murine lymphosarcoma virus (ABL) proteins; ABL-family proteins are highly conserved tyrosine kinases. Each ABL protein contains an SH3-SH2-TK (Src homology 3-Src homology 2-tyrosine kinase) domain cassette, which confers autoregulated kinase activity and is common among nonreceptor tyrosine kinases. Several types of posttranslational modifications control ABL catalytic activity, subcellular localization, and stability, with consequences for both cytoplasmic and nuclear ABL functions. Binding partners provide additional regulation of ABL catalytic activity, substrate specificity, and downstream signaling. By combining this cassette with actin-binding and -bundling domain, ABL proteins are capable of connecting phosphoregulation with actin-filament reorganization. Vertebrate paralogs, ABL1 and ABL2, have evolved to perform specialized functions. ABL1 includes nuclear localization signals and a DNA binding domain which is used to mediate DNA damage-repair functions, while ABL2 has additional binding capacity for actin and for microtubules to enhance its cytoskeletal remodeling functions. SH2 is involved in several autoinhibitory mechanism that constrain the enzymatic activity of the ABL-family kinases. In one mechanism SH2 and SH3 cradle the kinase domain while a cap sequence stabilizes the inactive conformation resulting in a locked inactive state. Another involves phosphatidylinositol 4,5-bisphosphate (PIP2) which binds the SH2 domain through residues normally required for phosphotyrosine binding in the linker segment between the SH2 and kinase domains. The SH2 domain contributes to ABL catalytic activity and target site specificity. It is thought that the ABL catalytic site and SH2 pocket have coevolved to recognize the same sequences. Recent work now supports a hierarchical processivity model in which the substrate target site most compatible with ABL kinase domain preferences is phosphorylated with greatest efficiency. If this site is compatible with the ABL SH2 domain specificity, it will then reposition and dock in the SH2 pocket. This mechanism also explains how ABL kinases phosphorylates poor targets on the same substrate if they are properly positioned and how relatively poor substrate proteins might be recruited to ABL through a complex with strong substrates that can also dock with the SH2 pocket. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1040660804 422 KKVWYASGCDRKTAEdALIRSAKDGSFLLRKSSGVDAQqpYTLVVFYNSRVYNIPVRYIASTKQYSlgkekQGEERFSSV 501
Cdd:cd09935     2 KHSWYHGPISRNAAE-YLLSSGINGSFLVRESESSPGQ--YSISLRYDGRVYHYRISEDSDGKVYV-----TQEHRFNTL 73

                          90
                  ....*....|....*...
gi 1040660804 502 CDMIENHQKNPLVLVDSL 519
Cdd:cd09935    74 AELVHHHSKNADGLITTL 91

Src homology 2 (SH2) domain; In general, SH2 domains are involved in signal transduction; they bind pTyr-containing polypeptide ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites. They are present in a wide array of proteins including: adaptor proteins (Nck1, Crk, Grb2), scaffolds (Slp76, Shc, Dapp1), kinases (Src, Syk, Fps, Tec), phosphatases (Shp-1, Shp-2), transcription factors (STAT1), Ras signaling molecules (Ras-Gap), ubiquitination factors (c-Cbl), cytoskeleton regulators (Tensin), signal regulators (SAP), and phospholipid second messengers (PLCgamma), amongst others.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1040660804 425 WYASGCDRKTAEDALiRSAKDGSFLLRKSSgvDAQQPYTLVVFYNS-RVYNIPVRYIASTKQYSLGKEKqgeeRFSSVCD 503
Cdd:cd00173     2 WFHGSISREEAERLL-RGKPDGTFLVRESS--SEPGDYVLSVRSGDgKVKHYLIERNEGGYYLLGGSGR----TFPSLPE 74

                  ....*
gi 1040660804 504 MIENH 508
Cdd:cd00173    75 LVEHY 79

C-terminal Src homology 2 (C-SH2) domain in Phospholipase C gamma; Phospholipase C gamma is a signaling molecule that is recruited to the C-terminal tail of the receptor upon autophosphorylation of a highly conserved tyrosine. PLCgamma is composed of a Pleckstrin homology (PH) domain followed by an elongation factor (EF) domain, 2 catalytic regions of PLC domains that flank 2 tandem SH2 domains (N-SH2, C-SH2), and ending with a SH3 domain and C2 domain. N-SH2 SH2 domain-mediated interactions represent a crucial step in transmembrane signaling by receptor tyrosine kinases. SH2 domains recognize phosphotyrosine (pY) in the context of particular sequence motifs in receptor phosphorylation sites. Both N-SH2 and C-SH2 have a very similar binding affinity to pY. But in growth factor stimulated cells these domains bind to different target proteins. N-SH2 binds to pY containing sites in the C-terminal tails of tyrosine kinases and other receptors. Recently it has been shown that this interaction is mediated by phosphorylation-independent interactions between a secondary binding site found exclusively on the N-SH2 domain and a region of the FGFR1 tyrosine kinase domain. This secondary site on the SH2 cooperates with the canonical pY site to regulate selectivity in mediating a specific cellular process. C-SH2 binds to an intramolecular site on PLCgamma itself which allows it to hydrolyze phosphatidylinositol-4,5-bisphosphate into diacylglycerol and inositol triphosphate. These then activate protein kinase C and release calcium. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1040660804 423 KVWYASGCDRKTAEDALIRSAKDGSFLLRKSSGvdaqqpytlvvfyNSRVYNIPVRYIASTKQYSLGKEKQ----GEERF 498
Cdd:cd09932     4 KEWFHANLTREQAEEMLMRVPRDGAFLVRPSET-------------DPNSFAISFRAEGKIKHCRIKQEGRlfviGTSQF 70

                          90       100       110
                  ....*....|....*....|....*....|....*.
gi 1040660804 499 SSVCDMIENHQKNPLVlvdslsntkDSTKLRHAVKP 534
Cdd:cd09932    71 ESLVELVSYYEKHPLY---------RKIKLRYPVNE 97

Src homology 2 (SH2) domain found in alpha2-chimerin and beta2-chimerin proteins; Chimerins are a family of phorbol ester- and diacylglycerol-responsive GTPase-activating proteins. Alpha1-chimerin (formerly known as n-chimerin) and alpha2-chimerin are alternatively spliced products of a single gene, as are beta1- and beta2-chimerin. alpha1- and beta1-chimerin have a relatively short N-terminal region that does not encode any recognizable domains, whereas alpha2- and beta2-chimerin both include a functional SH2 domain that can bind to phosphotyrosine motifs within receptors. All of the isoforms contain a GAP domain with specificity in vitro for Rac1 and a diacylglycerol (DAG)-binding C1 domain which allows them to translocate to membranes in response to DAG signaling and anchors them in close proximity to activated Rac. Other C1 domain-containing diacylglycerol receptors including: PKC, Munc-13 proteins, phorbol ester binding scaffolding proteins involved in Ca2+-stimulated exocytosis, and RasGRPs, diacylglycerol-activated guanine-nucleotide exchange factors (GEFs) for Ras and Rap1. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 1040660804 431 DRKTAEdALIRSAKDGSFLLRKSSGVDAQqpYTLVVFYNSRVYNIPVRYIASTKQYSLgkekqGEERFSSVCDMI 505
Cdd:cd10352    14 SREEAE-QLLSGASDGSYLIRESSRDDGY--YTLSLRFNGKVKNYKLYYDGKNHYHYV-----GEKRFDTIHDLV 80

Src homology 2 (SH2) domain found in SH2-containing inositol-5'-phosphatase (SHIP) and SLAM-associated protein (SAP); The SH2-containing inositol-5'-phosphatase, SHIP (also called SHIP1/SHIP1a), is a hematopoietic-restricted phosphatidylinositide phosphatase that translocates to the plasma membrane after extracellular stimulation and hydrolyzes the phosphatidylinositol-3-kinase (PI3K)-generated second messenger PI-3,4,5-P3 (PIP3) to PI-3,4-P2. As a result, SHIP dampens down PIP3 mediated signaling and represses the proliferation, differentiation, survival, activation, and migration of hematopoietic cells. PIP3 recruits lipid-binding pleckstrin homology(PH) domain-containing proteins to the inner wall of the plasma membrane and activates them. PH domain-containing downstream effectors include the survival/proliferation enhancing serine/threonine kinase, Akt (protein kinase B), the tyrosine kinase, Btk, the regulator of protein translation, S6K, and the Rac and cdc42 guanine nucleotide exchange factor, Vav. SHIP is believed to act as a tumor suppressor during leukemogenesis and lymphomagenesis, and may play a role in activating the immune system to combat cancer. SHIP contains an N-terminal SH2 domain, a centrally located phosphatase domain that specifically hydrolyzes the 5'-phosphate from PIP3, PI-4,5-P2 and inositol-1,3,4,5- tetrakisphosphate (IP4), a C2 domain, that is an allosteric activating site when bound by SHIP's enzymatic product, PI-3,4-P2; 2 NPXY motifs that bind proteins with a phosphotyrosine binding (Shc, Dok 1, Dok 2) or an SH2 (p85a, SHIP2) domain; and a proline-rich domain consisting of four PxxP motifs that bind a subset of SH3-containing proteins including Grb2, Src, Lyn, Hck, Abl, PLCg1, and PIAS1. The SH2 domain of SHIP binds to the tyrosine phosphorylated forms of Shc, SHP-2, Doks, Gabs, CD150, platelet-endothelial cell adhesion molecule, Cas, c-Cbl, immunoreceptor tyrosine-based inhibitory motifs (ITIMs), and immunoreceptor tyrosine-based activation motifs (ITAMs). The X-linked lymphoproliferative syndrome (XLP) gene encodes SAP (also called SH2D1A/DSHP) a protein that consists of a 5 residue N-terminus, a single SH2 domain, and a short 25 residue C-terminal tail. XLP is characterized by an extreme sensitivity to Epstein-Barr virus. Both T and natural killer (NK) cell dysfunctions have been seen in XLP patients. SAP binds the cytoplasmic tail of Signaling lymphocytic activation molecule (SLAM), 2B4, Ly-9, and CD84. SAP is believed to function as a signaling inhibitor, by blocking or regulating binding of other signaling proteins. SAP and the SAP-like protein EAT-2 recognize the sequence motif TIpYXX(V/I), which is found in the cytoplasmic domains of a restricted number of T, B, and NK cell surface receptors and are proposed to be natural inhibitors or regulators of the physiological role of a small family of receptors on the surface of these cells. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1040660804 425 WYASGCDRKTAEDALIRSAKDGSFLLRKSSGVdaQQPYTLVVFYNSRVYN---IPVRYIASTKQYSLGKEKQgeeRFSSV 501
Cdd:cd10343     5 WYHGNITRSKAEELLSKAGKDGSFLVRDSESV--SGAYALCVLYQNCVHTyriLPNAEDKLSVQASEGVPVR---FFTTL 79

                          90
                  ....*....|....*...
gi 1040660804 502 CDMIENHQKNPLVLVDSL 519
Cdd:cd10343    80 PELIEFYQKENMGLVTHL 97

Sterile alpha motif; Widespread domain in signalling and nuclear proteins. In EPH-related tyrosine kinases, appears to mediate cell-cell initiated signal transduction via the binding of SH2-containing proteins to a conserved tyrosine that is phosphorylated. In many cases mediates homodimerisation.

                           10        20        30        40        50        60
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1040660804   10 EGWSPAQVASFLNQNNMRECAEAVQRNRIDGGRLLTL-SDSDLNKF---SFIHRpqlQKIVQDIKK 71
Cdd:smart00454   2 SQWSPESVADWLESIGLEQYADNFRKNGIDGALLLLLtSEEDLKELgitKLGHR---KKILKAIQK 64

Src homology 2 (SH2) domain found in suppressor of cytokine signaling (SOCS) family; SH2 domain found in SOCS proteins. SOCS was first recognized as a group of cytokine-inducible SH2 (CIS) domain proteins comprising eight family members in human (CIS and SOCS1-SOCS7). In addition to the SH2 domain, SOCS proteins have a variable N-terminal domain and a conserved SOCS box in the C-terminal domain. SOCS proteins bind to a substrate via their SH2 domain. The prototypical members, CIS and SOCS1-SOCS3, have been shown to regulate growth hormone signaling in vitro and in a classic negative feedback response compete for binding at phosphotyrosine sites in JAK kinase and receptor pathways to displace effector proteins and target bound receptors for proteasomal degradation. Loss of SOCS activity results in excessive cytokine signaling associated with a variety of hematopoietic, autoimmune, and inflammatory diseases and certain cancers. Members (SOCS4-SOCS7) were identified by their conserved SOCS box, an adapter motif of 3 helices that associates substrate binding domains, such as the SOCS SH2 domain, ankryin, and WD40 with ubiquitin ligase components. These show limited cytokine induction. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1040660804 424 VWYASGCDRKTAEDALiRSAKDGSFLLRKSSgvDAQQPYTLVVfynsRVYNIP--VRYIASTKQYSLGKEKQGEERFSSV 501
Cdd:cd09923     1 GWYWGGITRYEAEELL-AGKPEGTFLVRDSS--DSRYLFSVSF----RTYGRTlhARIEYSNGRFSFDSSDPSVPRFPCV 73

                  ....*.
gi 1040660804 502 CDMIEN 507
Cdd:cd09923    74 VELIEH 79

SAM domain (Sterile alpha motif); It has been suggested that SAM is an evolutionarily conserved protein binding domain that is involved in the regulation of numerous developmental processes in diverse eukaryotes. The SAM domain can potentially function as a protein interaction module through its ability to homo- and heterooligomerise with other SAM domains.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 1040660804  10 EGWSPAQVASFLNQNNMRECAEAVQRNRIDGGRLLTLSDSDLNKF---SFIHRpqlQKIVQDIKK 71
Cdd:pfam00536   1 DGWSVEDVGEWLESIGLGQYIDSFRAGYIDGDALLQLTEDDLLKLgvtLLGHR---KKILYAIQR 62

SAM domain of diacylglycerol kinase delta and eta subunits; SAM (sterile alpha motif) domain of DGK-eta-delta subfamily proteins is a protein-protein interaction domain. Proteins of this subfamily are multidomain diacylglycerol kinases with a SAM domain located at the C-terminus. DGK proteins participate in signal transduction. They regulate the level of second messengers such as diacylglycerol and phosphatidic acid. The SAM domain of DGK proteins can form high molecular weight homooligomers through head-to-tail interactions as well as heterooligomers between the SAM domains of DGK delta and eta proteins. The oligomerization plays a role in the regulation of DGK intracellular localization.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*....
gi 1040660804  12 WSPAQVASFLNQNNMRECAEAVQRNRIDGGRLLTLSDSDLNKFSFIHRPQLQKIVQDIK 70
Cdd:cd09507     5 WTTEEVGAWLESLQLGEYRDIFARNDIRGSELLHLERRDLKDLGITKVGHVKRILQAIK 63

SAM domain of sphingomyelin synthase related subfamily; SAM (sterile alpha motif) domain of SGMS-like (sphingomyelin synthase) subfamily is a potential protein-protein interaction domain. This group of proteins is related to sphingomyelin synthase 1, and contains an N-terminal SAM domain. The function of SGMS1-like proteins is unknown; they may play a role in sphingolipid metabolism.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1040660804  10 EGWSPAQVASFLNQNNMRECAEA-VQRNRIDGGRLLTLSDSDLnkfsfiHRPQLQ-KIVQDIKKnddsLFNRIKRFQNE 86
Cdd:cd09515     2 HEWTCEDVAKWLKKEGFSKYVDLlCNKHRIDGKVLLSLTEEDL------RSPPLEiKVLGDIKR----LWLAIRKLQRQ 70

SAM domain of Polycomb group; SAM (sterile alpha motif) domain of Polycomb group is a protein-protein interaction domain. The Polycomb group includes transcriptional repressors which are involved in the regulation of some key regulatory genes during development in many organisms. They are best known for silencing Hox (Homeobox) genes. Polycomb proteins work together in large multimeric and chromatin-associated complexes. They organize chromatin of the target genes and maintain repressed states during many cell divisions. Polycomb proteins are classified based on their common function, but not on conserved domains and/or motifs; however many Polycomb proteins (members of PRC1 class complex) contain SAM domains which are more similar to each other inside of the Polycomb group than to SAM domains outside of it. Most information about structure and function of Polycomb SAM domains comes from studies of Ph (Polyhomeotic) and Scm (Sex comb on midleg) proteins. Polycomb SAM domains usually can be found at the C-terminus of the proteins. Some members of this group contain, in addition to the SAM domain, MTB repeats, Zn finger, and/or DUF3588 domains. Polycomb SAM domains can form homo- and/or heterooligomers through ML and EH surfaces. SAM/SAM oligomers apparently play a role in transcriptional repression through polymerization along the chromosome. Polycomb proteins are known to be highly expressed in some cells years before their cancer pathology; thus they are attractive markers for early cancer therapy.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|.
gi 1040660804  12 WSPAQVASFLNQNNM-RECAEAVQRNRIDGGRLLTLSDSDL 51
Cdd:cd09509     4 WSVDDVAQFIKSLDGcAEYAEVFREQEIDGQALLLLTEDDL 44

SAM domain of WDSUB1 proteins; SAM (sterile alpha motif) domain of WDSUB1 subfamily proteins is a putative protein-protein interaction domain. Proteins of this group contain multiple domains: SAM, one or more WD40 repeats and U-box (derived version of the RING-finger domain). Apparently the WDSUB1 subfamily proteins participate in protein degradation through ubiquitination, since U-box domain are known as a member of E3 ubiquitin ligase family, while SAM and WD40 domains most probably are responsible for an E2 ubiquitin-conjugating enzyme binding and a target protein binding.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1040660804  10 EGWSPAQVASFLNQNNMRECAEAVQRNRIDGGRLLTLSD----SDLNKFSFIHRPQLQKIVQDIKKNDDS 75
Cdd:cd09505     3 QDWSEEDVCTWLRSIGLEQYVEVFRANNIDGKELLNLTKeslsKDLKIESLGHRNKILRKIEELKMKSDS 72

N-terminal Src homology 2 (SH2) domain found in Ras GTPase-activating protein 1 (GAP); RasGAP is part of the GAP1 family of GTPase-activating proteins. The protein is located in the cytoplasm and stimulates the GTPase activity of normal RAS p21, but not its oncogenic counterpart. Acting as a suppressor of RAS function, the protein enhances the weak intrinsic GTPase activity of RAS proteins resulting in RAS inactivation, thereby allowing control of cellular proliferation and differentiation. Mutations leading to changes in the binding sites of either protein are associated with basal cell carcinomas. Alternative splicing results in two isoforms. The shorter isoform which lacks the N-terminal hydrophobic region, has the same activity, and is expressed in placental tissues. In general the longer isoform contains 2 SH2 domains, a SH3 domain, a pleckstrin homology (PH) domain, and a calcium-dependent phospholipid-binding C2 domain. The C-terminus contains the catalytic domain of RasGap which catalyzes the activation of Ras by hydrolyzing GTP-bound active Ras into an inactive GDP-bound form of Ras. This model contains the N-terminal SH2 domain. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1040660804 425 WYASGCDRKTAEDALIRSAKDGSFLLRKSSgvdaQQPYTLVVFYNSRVYNIPVRYIASTKQYSLGKekqgeERFSSVCDM 504
Cdd:cd10353    21 WYHGRLDRTIAEERLRQAGKLGSYLIRESD----RRPGSFVLSFLSRTGVNHFRIIAMCGDYYIGG-----RRFSSLSDL 91

                  .
gi 1040660804 505 I 505
Cdd:cd10353    92 I 92

Src homology 2 domain found in Growth factor receptor-bound protein 2 (Grb2) and similar proteins; The adaptor proteins here include homologs Grb2 in humans, Sex muscle abnormal protein 5 (Sem-5) in Caenorhabditis elegans, and Downstream of receptor kinase (drk) in Drosophila melanogaster. They are composed of one SH2 and two SH3 domains. Grb2/Sem-5/drk regulates the Ras pathway by linking the tyrosine kinases to the Ras guanine nucleotide releasing protein Sos, which converts Ras to the active GTP-bound state. The SH2 domain of Grb2/Sem-5/drk binds class II phosphotyrosyl peptides while its SH3 domain binds to Sos and Sos-derived, proline-rich peptides. Besides it function in Ras signaling, Grb2 is also thought to play a role in apoptosis. Unlike most SH2 structures in which the peptide binds in an extended conformation (such that the +3 peptide residue occupies a hydrophobic pocket in the protein, conferring a modest degree of selectivity), Grb2 forms several hydrogen bonds via main chain atoms with the side chain of +2 Asn. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1040660804 425 WYASGCDRKTAEDALIRSAKDGSFLLRKSSgvdaQQPYTlvvfynsrvYNIPVRYIASTKQYSLGKEKQGE-----ERFS 499
Cdd:cd09941     5 WFHGKISRAEAEEILMNQRPDGAFLIRESE----SSPGD---------FSLSVKFGNDVQHFKVLRDGAGKyflwvVKFN 71

                          90       100
                  ....*....|....*....|....
gi 1040660804 500 SVCDMIENHQKNP------LVLVD 517
Cdd:cd09941    72 SLNELVDYHRTTSvsrnqqIFLRD 95

SAM domain of Scm-like-3MBT3,4 proteins of Polycomb group; SAM (sterile alpha motif) domain of Scm-like-3MBT3,4 (Sex comb on midleg, Malignant brain tumor) subfamily proteins (also known as L3mbtl3,4 proteins) is a putative protein-protein interaction domain. Proteins of this subfamily are predicted transcriptional regulators belonging to Polycomb group. The majority of them are multidomain proteins: in addition to the C-terminal SAM domain, they contain three MBT repeats and Zn finger domain. Murine L3mbtl3 protein of this subfamily is essential for maturation of myeloid progenitor cells during differentiation. Human L3mbtl4 is a potential tumor suppressor gene in breast cancer, while deregulation of L3MBTL3 is associated with neuroblastoma.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 1040660804  11 GWSPAQVASFLNQ-NNMRECAEAVQRNRIDGGRLLTLSDSDLNKFSFIhrpqlqKIVQDIKknddsLFNRIKRF 83
Cdd:cd09582     3 RWSVDEVAEFVQSlPGCEEHAKVFRDEQIDGEAFLLLTQSDLVKILGI------KLGPALK-----IYNSILML 65

SAM domain of HD-phosphohydrolase; SAM (sterile alpha motif) domain of SAM_HD subfamily proteins is a putative protein-protein interaction domain. Proteins of this group, additionally to the SAM domain, contain a HD hydrolase domain. Human SAM-HD1 is a nuclear protein involved in innate immune response and may act as a negative regulator of the cell-intrinsic antiviral response. Mutations in this gene lead to Aicardi-Goutieres syndrome (symptoms include cerebral atrophy, leukoencephalopathy, hepatosplenomegaly, and increased production of alpha-interferon).

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                  ....*....|....*....|....*....|....*....|....
gi 1040660804  12 WSPAQVASFLNQNNMR--ECAEAVQRNRIDGGRLLTLSDSDLNK 53
Cdd:cd09508     5 WDPEDVCQFLRGNGFGepELLEIFRENEITGAHLPDLTESRLEK 48